Abstract

Background

International travel plays a role in the spread of HIV-1 across Europe. It is, however,
not known whether international travel is more important for spread of the epidemic
as compared to endogenous infections within single countries. In this study, phylogenetic
associations among HIV of newly diagnosed patients were determined across Europe.

Results

Data came from the SPREAD programme which collects samples of newly diagnosed patients
that are representative for national HIV epidemics. 4260 pol sequences from 25 European
countries and Israel collected in 2002–2007 were included.

We identified 457 clusters including 1330 persons (31.2% of all patients). The cluster
size ranged between 2 and 28. A number of 987 patients (74.2%) were part of a cluster
that consisted only of patients originating from the same country. In addition, 135
patients (10.2%) were in a cluster including only individuals from neighboring countries.
Finally, 208 patients (15.6%) clustered with individuals from countries without a
common border. Clustering with patients from the same country was less prevalent in
patients being infected with B subtype (P-value <0.0001), in men who have sex with men (P-value <0.0001), and in recently infected patients (P-value =0.045).

Conclusions

Our findings indicate that the transmission of HIV-1 in Europe is predominantly occurring
between patients from the same country. This could have implications for HIV-1 transmission
prevention programmes. Because infections through travelling between countries is
not frequently observed it is important to have good surveillance of the national
HIV-1 epidemics.